This is the first build with the failure.
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.10%20Tests/32955
(ignore the other four chromedriver_py test failures; that's a separate issue; see https://chromium-review.googlesource.com/c/chromium/src/+/1095674)

Those two tests have been failing consistently since then.

I don't see anything in the blame list that seems like a cause.


======================================================================
ERROR: testGetSessions (__main__.SessionHandlingTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "../../chrome/test/chromedriver/test/run_py_tests.py", line 2583, in testGetSessions
    response = driver2.GetSessions()
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/chromedriver.py", line 343, in GetSessions
    return self.ExecuteCommand(Command.GET_SESSIONS)
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/chromedriver.py", line 298, in ExecuteCommand
    response = self._ExecuteCommand(command, params)
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/chromedriver.py", line 288, in _ExecuteCommand
    response = self._executor.Execute(command, params)
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/command_executor.py", line 197, in Execute
    response = self._http_client.getresponse()
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 1121, in getresponse
    response.begin()
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 438, in begin
    version, status, reason = self._read_status()
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 402, in _read_status
    raise BadStatusLine(line)
BadStatusLine: ''
======================================================================
ERROR: testQuitASessionMoreThanOnce (__main__.SessionHandlingTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "../../chrome/test/chromedriver/test/run_py_tests.py", line 2573, in testQuitASessionMoreThanOnce
    driver = self.CreateDriver()
  File "../../chrome/test/chromedriver/test/run_py_tests.py", line 294, in CreateDriver
    **kwargs)
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/chromedriver.py", line 237, in __init__
    response = self._ExecuteCommand(Command.NEW_SESSION, params)
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/chromedriver.py", line 288, in _ExecuteCommand
    response = self._executor.Execute(command, params)
  File "/b/s/w/ir/chrome/test/chromedriver/test/../client/command_executor.py", line 196, in Execute
    self._http_client.request(command[0], '/'.join(substituted_parts), body)
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 1042, in request
    self._send_request(method, url, body, headers)
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 1082, in _send_request
    self.endheaders(body)
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 1038, in endheaders
    self._send_output(message_body)
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 882, in _send_output
    self.send(msg)
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 844, in send
    self.connect()
  File "/b/s/w/ir/.swarming_module/lib/python2.7/httplib.py", line 821, in connect
    self.timeout, self.source_address)
  File "/b/s/w/ir/.swarming_module/lib/python2.7/socket.py", line 575, in create_connection
    raise err


Incidentally, the flakiness dashboard is confusing.  It makes it look like they've been failing consistently since they were enabled.  I don't think that's the case.  (In the runs before the run linked above, those tests were run and succeeded.)
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=chromedriver_py_tests&tests=testGetSessions%2CtestQuitASessionMoreThanOnce